Metabolic syndrome has become one of the leading health problems in the world. As a component of metabolic syndrome, obesity also has causal roles in other components of the syndrome, including insulin resistance, dyslipidemia, and cardiovascular diseases. Effective treatments for metabolic syndrome in general and obesity in particular have been lacking. Effective therapies for the treatment of obesity, a key element of metabolic syndrome, are urgently needed.
A number of mammalian stearoyl-coenzyme A desaturase (SCD) genes have been cloned. For example, two genes have been cloned from rat (SCD1, SCD2) and four SCD genes have been isolated from mouse (SCD1, 2, 3, and 4). While the basic biochemical role of SCD has been known in rats and mice since the 1970's (see, e.g., Jeffcoat, R. et al., Elsevier Science, Vol. 4, pp. 85-112, 1984; de Antueno, R J, Lipids, Vol. 28, No. 4, pp. 285-290, 1993), it has only recently been directly implicated in human disease processes.
A single SCD gene, stearoyl-coenzyme A desaturase-1 (SCD1) has been characterized in humans. SCD1 is described in, e.g., International Publication No. application, WO 01/62954. A second human SCD isoform has recently been identified, and because it bears little sequence homology to alternate mouse or rat isoforms it has been named human SCD5 or hSCD5 (see, e.g., International Publication No. WO 02/26944).
SCD-1 catalyzes conversion of saturated fatty acids, stearoyl-CoA and palmitoyl-CoA, to monounsaturated fatty acids, oleoyl-CoA and pamitoleoyl-CoA, respectively. These fatty acids are components of membrane phospholipids, triglycerides, and cholesterol esters. Changes in SCD activity ultimately change membrane fluidity, lipoprotein metabolism, and adiposity. SCD-1 inhibition can lead to decreased adiposity and thus be a potential therapy for metabolic syndrome.
Since obesity is becoming increasingly prevalent worldwide, much effort is being devoted to understanding its pathogenesis and treatment. In recent years, several candidate genes have been proposed as therapeutic targets. However, stearoyl-CoA desaturase 1 is of special significance, because it is the major gene target of leptin—a central mediator of energy homeostasis. There is evidence that SCD1 deficiency activates metabolic pathways that promote b-oxidation and decrease lipogenesis in liver and skeletal muscles. One mechanism is via increased activation of AMP-activated protein kinase. SCD1 mutation results also in global changes in expression of genes involved in lipid metabolism. SCD1 deficient mice have increased energy expenditure, reduced body adiposity, and are resistant to diet-induced obesity.
Thus, SCD1 inhibition represents a new and important target for the treatment of various disorders such as obesity and related metabolic disorders. Accordingly, there is a need in the art for derivatives that act as inhibitors of stearoyl-CoA desaturase, such as SCD1.